As is known, crude potash salts can be separated into their main components by means of electrostatic separation. The principle of such separating processes is described, for example, in "Ullmann's Eancyklopaedie der technischen Chemie", 4. Auflage, Bd. 13 (1977), pages 477 to 479. In accordance therewith the crushed crude potash salt after chemical conditioning under heat is triboelectrically charged and is subsequently fed in a free fall through the electrical field of a so-called electrostatic free fall separator, which is mostly designed as a free fall tube separator. The movement of the particles in the electrical field of the separator is determined by the horizontally acting attraction force and the vertically directed gravitational force. This results in more or less curved course of fall of the individual particles of the components of the crude potash salt, which have a tendency to move toward the oppositely charged electrode. In order to prevent at the lower end of the electric field a remixing of the particles of the components of the crude potash salts which were separated in the aforementioned manner, there are arranged pivotable flow splitting blades made from electrically insulating material. The blades include with the vertical an acute angle opening toward the electrical field. Between these blades a middling material is collected whose particles have experienced only a small or no deflection in the electrical field. By the position of these flow splitting blades the amount and composition of the valuable substance concentrate and of the middling material can be influenced in the same way as the amount and composition of the separated residue.
The result of the electrostatic separation of the crude potash salts can be influenced and optimized by the adjustment of the incline of the separating blades. For this purpose, the contents of predetermined components in the valuable substance concentrate and in the residue were determined to serve as guiding magnitudes and thereafter the incline of the separating blades was adjusted manually in order to obtain an optimum separating result, namely a high enrichment in the valuable substance concentrate, and to receive a residue which is substantially free of valuable substances. This prior art manual adjustment of the incline of the separating blades is time consuming and substantially depends from the experience of the operating personnel and is subjected to numerous possibilities of error.